As data tracks on magnetic tape become narrower, the challenge to properly track head location relative to such tape increases significantly. One factor of interest relates to tape dimensional stability. One effective method to mitigate tape dimensional stability is to space channels (or data tracks) on the recording head closer together. However, as write elements are positioned closer to one another, such elements can electromagnetically interfere with one another during a write operation. One write element that receives electronic instructions to write a particular data pattern on a track may experience an electromagnetic interference (EMI) condition (or “cross-talk”) from neighboring write elements thereby changing (generally degrading) the data pattern. Such cross-talk may limit the proximity that the write elements are positioned with respect to one another.
Cross-talk may be quantified in one way by (i) obtaining a measurement of a Viterbi Quality Metric (VQM) when all of the write elements are writing the same data pattern on the tape (ii) obtaining another measurement of the VQM when all of the write elements are writing different data patterns, and (iii) comparing both VQM measurements (i.e., VQM measurement when writing the same data pattern and VQM measurement when writing different data patterns) to one another. The VQM measurement typically ranges from 0 to 1 where higher values are generally indicative of better channel quality.
In one example, VQM measurements were obtained on a driver with a 42.6μ channel pitch with data patterns that either suppress cross-talk (e.g., all channels having similar data patterns being written thereon), or encourages cross-talk (e.g., all channels having different data patterns being written thereto). The resulting VQM was observed to drop by about 0.1 for the data patterns that encourage cross-talk. Also, it is known that cross-talk generated during a write operation may cause a significant transition shift for writers on a small channel pitch as disclosed in “Crosstalk Between Write Transducers,” R. G. Biskeborn, P. Herget and P. O. Jubert, IEEE Trans Mag 44, No. 11, November 2008, p. 3625.
Tape dimensional stability generally corresponds to the notion of retaining a precise track to channel spacing such that an empty space is not left on the track or that data is not written on a corresponding track that was previously written to. While a small channel pitch may mitigate the effects of tape dimensional stability, the cross-talk generated at this channel pitch may be large.
With cross-talk, a magnetic field from a write element may be modeled as a dipole where the magnetic field drops by 1/d3, where d is the distance from the write element. Generally, if various write elements are far enough apart from one another, then the magnetic field drop (e.g., 1/d3) is substantial and the ensuing cross-talk between a plurality of write elements is small. However, if the write elements are positioned closer to one another, the cross-talk between such write elements increases. If the write elements are spaced twice as close together, one would expect to see eight times as much cross talk. In view of the foregoing, it is desirable to cancel cross-talk generated by write elements during a write operation.